1. Field of the Invention
The present invention relates to a method of surface treatment, a method for forming circuit lines, an apparatus for forming circuit lines, and a printed circuit board formed thereby.
2. Description of the Related Art
There are two kinds of conventional methods for forming circuit lines on a substrate of which one is a substractive process forming circuit lines by etching a copper layer and the other is an additive process forming circuit lines by plating with copper on a bare dielectric material. Both methods require a photoresist film for forming a circuit pattern on a substrate, and exposure and development steps of the photoresist film. Especially, the substractive process requires a longer etching step of the copper layer. These methods have some drawbacks: 1) the copper layer in the substractive process must be introduced to a whole space of the substrate, whether or not circuit lines are formed, so that it becomes costly and low efficient, and 2) these processes require the steps of providing a photoresist film and removing it later, so that the manufacturing time becomes longer and the manufacturing process becomes complicate and inefficient. Further, these processes cannot provide fine circuit lines.
To overcome the drawbacks associated with above mentioned conventional processes, a method for forming fine circuit lines is suggested by an inkjet process, which forms circuit lines by applying a conductive ink on a substrate in accordance with a circuit pattern. The method for forming fine circuit lines by the ink-jet process does not require a photoresist film or an etching step, and can form fine circuit lines. However, it also has a drawback that a bonding power between the substrate and the circuit lines is weak, so that it deteriorates an electric reliability.
To solve the defects associated with the method for forming fine circuit lines by the ink-jet process, referring to FIG. 1, it shows cross-sectional views of a substrate for forming circuit lines on a printed circuit board by using a laser beam. This laser process for forming conductive circuit lines comprises the steps for forming a waterproofing layer 150 on a whole surface of a base film 110, removing the waterproofing layer by the laser beam in accordance with a circuit pattern, and applying a conductive ink 170 on parts of a substrate where the waterproofing layer is removed. The laser process requires an extra apparatus of generating the laser beam which is expensive and the extra steps for forming and removing the waterproofing layer, so that it becomes inconvenient and inefficient.
It would therefore be desirable to have an improved method for forming fine circuit lines and printed circuit board made thereby.